1. Field of the Invention
This invention relates to a device for making hot beverages by extraction, particularly for making coffee, with at least one metering device for a powdered beverage, a hot water preparation element and a water pump, as well as an ejector for removing used powdered beverage from a movable extraction cup, which can be fastened on a movable holder which is situated in a guide track and can therefore bring the extraction cup into a position in which it comes into operational engagement with an extraction piston.
2. Description of Prior Art
A device of the above mentioned type is known, for example, from Swiss Patent Reference CH-A-681198. The device described therein describes a particular kind of guidance of the extraction cup in a horizontal and a vertical movement, which results in a particularly simple construction of the coffee maker. The machines of interest here are machines predominantly used in households, which must be designed considerably more simply and cost-effectively than corresponding coffee makers for the restaurant business.
Particularly elaborate machines for restaurant use allow the variation of the strength of the extracted beverage. This requires adjustable metering of the powdered beverage and adaptation of the volume of the extraction cup, wherein the relative position of the extraction cup and of the extraction piston engaging it are adjustable as a function of the metered powdered beverage. In the commercially employed coffee machines mentioned, this relative displacement of the extraction cup and the extraction piston with respect to each other is performed by complex electronic controls and corresponding hydraulic or electric motor-driven displacement devices. The available spatial conditions on household machines for the preparation of hot beverages by extraction do not permit such elaborations.
Commercial coffee makers are usually equipped with a grinder which is driven at a constant speed. The ground coffee is moved from the grinder directly to the extraction cup. A timer control meters the amount of coffee which is placed into the extraction cup. As a rule, the starting of the motor of the grinder is controlled. Given the already mentioned requirement that the motor run at constant rotational speed, it is possible to meter the amount of ground powdered coffee by changing the switch-on time. To transfer this concept to household coffee makers is impractical because of the costs associated with an elaborate, rotational speed monitored induction motor.
Metering devices are often used in connection with the devices of the previously mentioned type for household use which pass on the ground powdered beverage in a fixed amount to the extraction cup. A device for metering powdered coffee is known from French Patent Reference FR-A1518759, wherein the grinder places the ground powdered coffee directly into a metering chamber which has a pressure-sensitive elastically deformable wall element on which a signal transmitter is disposed, which generates a signal as a function of the elastic deformation of the wall element. Another embodiment of such a metering device is disclosed in European Patent Reference EP-A-139964, wherein the wall element is a pressure-sensitive elastically deformable diaphragm which, when the desired fill level has been attained, acts on a signal transmitter which simultaneously unlocks a pivotal bottom element.
French Patent Reference FR-A-2301214 also shows such a metering device, wherein the grinder passes the ground powdered beverage directly into two metering chambers of different sizes. Each metering chamber again has a movable wall acting on a signal transmitter. The position of the movable walls can be changed and set over a minimal range with a screw driver and a counter nut. However, this adjustment is performed at the factory and is later sealed and cannot be affected by the user of the device.
With the known devices for the preparation of hot beverages, in particular coffee, of the previously mentioned type, the extraction cup and extraction piston assume a defined fixed position with respect to each other when they are in the brewing position.
It is known that in the course of the extraction process the powdered beverage expands. Accordingly, it has been proposed to seat the filter plate in the extraction cup movably and to interpose a spring. The movement of the powdered beverage during expansion can be intercepted in this way. Such solutions are disclosed in European Patent Reference EP-A-486434 and German Patent Reference DE-U-9214283, for example.